Construction National 1CHG (WINTER 2015/16)

Page 15

Building durable structures [ THE MOST USED man-made

A magnified image showing crystals growing within concrete treated with integral crystalline waterproofing


More times than not, the selection is narrowed down to the surface or material on the planet is concrete. All external membrane and the internal construction projects – small, medium membrane using crystalline technology. and large – have used concrete in one The external membrane is a material way or another. that provides a barrier around the However, as evidenced by crumbling concrete structure in order to prevent infrastructure and structures the the passage of water. Externally world over, the quality of the concrete applied membranes are the traditional can determine whether a project waterproofing method, but they is truly viable or not. For example, have limitations that include tears, building a bridge with a lifespan of punctures, deterioration over time and 50 years is not economically viable installation errors. If any of these occur, when you consider the cost of initial repair can be impossible because the construction, eventual repairs and the membrane is not accessible through likelihood of early replacement. the concrete and it is hard to find the Thus, the lifespan of a failed area that needs to be fixed. This concrete structure is vital. With ends in replacement which, if possible population growth and density of at all, involves a great deal of time and cities intensifying, constructing considerable expense. replacements of key infrastructure An internal or integral waterproofing and buildings can be a costly and membrane is one that performs sometimes impossible process. its function within the concrete as Where it is possible, it creates huge opposed to on the surface. This is disruption to the local population. The the technology behind Permeability longer these structures can last, the Reducing Admixtures (PRA). The better. admixture becomes a permanent Concrete can deteriorate under a Crystalline waterproofing was used to protect the Greater solution as it is part of the concrete number of circumstances, including London Authority building adjacent to the Thames mix. It lays dormant in the matrix chloride attack/corrosion of steel until it comes in contact with moisture when it develops a needle-like reinforcement, sulphate attack, alkali aggregate reaction and freeze/ microstructure to stop the flow of moisture. thaw cycles. Furthermore, in North America the concrete waterproofing industry That being said, the most adverse influence on concrete durability redefined their terminology a short time ago in a way which helps involves the transport of fluids through the concrete. Water continues to clearly understand the differences between admixtures. In fact, to damage or completely destroy more buildings and structures the American Concrete Institute’s 212.3R-10 Report on Chemical than war or natural disasters. Of course, concrete does have water Admixture document devoted chapter 15 to Permeability Reducing resistant capabilities, but it is at risk to water penetration. Thus, a Admixtures and outlines PRAH and PRAN classifications. Permeability waterproofing barrier is a must to lower the permeability and increase Reducing Admixture – Hydrostatic Conditions, or PRAH products, are the durability of concrete. sufficiently able to resist water under hydrostatic pressure penetration To do so there are a few options in creating a concrete waterproof and are suitable for watertight construction. barrier, including crystalline admixtures; water repelling admixtures; Conversely, damproofing admixtures are now referred to as densifying admixtures; densifying admixtures and water reducers; and Permeability Reducing Admixture – Non-Hydrostatic Conditions surface-applied membranes. or PRAN. PRAN admixtures reduce water absorption by repellent chemicals (soap, oils) or partial pore blocking (densifiers). These admixtures are not suitable for concrete exposed to water under pressure and cannot protect in the presence of hydrostatic pressure. Waterproofing against hydrostatic pressure is an important distinction that sets PRAHs apart from PRANs. Crystalline waterproofing is the durable concrete waterproofing solution worldwide. With sustainable building practices increasing in importance, and the lifespan of a structure intrinsically connected to this development, a reliable waterproofing solution that will last for the intended life of the concrete structures becomes paramount. q • For more information contact Source One Environmental on 01226 397015, email contact@ or visit the website See also Michael T. Kubal’s Construction Waterproofing Handbook.